Studies were conducted to evaluate vacuole formation kinetics, the ability of vacuolated oocytes to exhibit germinal vesicle breakdown (GVBD) and the occurrence of vacuole remission. Oocytes were recovered from excised ovaries of unstimulated animals, without regard to menstrual cycle stage, by in vitro follicular rupture. The percentage of oocytes containing vacuoles increased from T0 (38%; 84/223) to T24 (50%; 125/251), but remained constant from T24 to T48 (51%; 128/253). The ability of vacuolated oocytes to undergo GVBD by T24 (15%; 9/59) and T48 (25%; 15/61) was reduced. Thus, nuclear maturation of vacuolated oocytes appears to be compromised in comparison to nonvacuolated counterparts at both 24 and 48 hrs post-collection. Vacuole remission does occur, albeit at very low levels, in rhesus monkey oocytes at both 24 and 48 hrs post-collection. Vacuole formation is not influenced by culture media, osmolarity or protein source, but is reduced by lowering culture temperature; however, oocyte quality is adversely affected by lowering temperature. We asked if vacuole formation was related to cyclic AMP changes that may precede GVBD. Results suggest no differences in vacuole formation rates or extents in the presence or absence of IBMX. We are left with the hypothesis that vacuole formation is secondary to events/responses triggered by removal of the ovary. Vacuole formation has been studied as a function of the collection technique. At 35 hr, 60% of intact oocytes recovered from unstimulated animals were vacuolated. When experiments were conducted on stimulated animals, one ovary was aspirated before removal and the other was removed and aspirated. Direct ovarian aspiration was associated with baseline levels of vacuole formation while the excised ovary produced oocytes that showed elevated vacuole formation levels. We have scheduled two more animals/repeats of this last experiment.